Northern Ireland and the Republic of Ireland have different currencies.
In the Republic of Ireland the currency used is the Euro and in Northern Ireland the currency used is the Pound Sterling.
Most visits to Ireland are trouble-free but you should be aware of the global risk of indiscriminate international terrorist attacks, which could be against civilian targets, including places frequented by foreigners.
Ireland is a parliamentary, representative democratic republic and a member state of the European Union. While the head of state is the popularly elected President of Ireland, this is a largely ceremonial position with real political power being vested in the indirectly elected Taoiseach (prime minister) who is the head of the government.